1. Technical Field
The present invention relates to a distance measuring device, and particularly to an optically distance measuring device and a method for optically measuring distance.
2. Description of the Related Art
Recently, a three dimension distance measuring device has been widely applied to measurement of distance. The measuring principle of a conventional three dimension distance measuring device is described as follows. A laser emitter emits a specific measuring light beam. An image sensor senses the specific measuring light beam to obtain the optical information (e.g., time, position, configuration, size, intensity, phase, etc.) of the specific measuring light beam. According to the optical information, the distances of various objects in the measuring range of the conventional three dimension distance measuring device can be obtained.
A measurable distance of the conventional distance measuring device is usually changeless. However, in practical processes of applying the conventional distance measuring device, it is necessary to change the measurable distance of the distance measuring device according to the various applying environments. Therefore, the conventional distance measuring device can not satisfy the demand of changing the measurable distance.
On the other hand, when the conventional distance measuring device is used to measure a far object, the energy of the light beam irradiating the far object is poor. Thus, it is necessary for the conventional distance device to be equipped with a high power light emitting component so that the conventional distance device has a far measurable distance. However, equipping with the high power light emitting component will increase the cost of the conventional distance measuring device, and further will not benefit for saving energy resources and environmental protection.